Synthesis and ring opening reactions of tetrahydroimidazo-[1,5-b][1,2,4]oxadiazol-2(1H)-thiones

Abstract

1,3-Dipolar cycloaddition of imidazoline 3-oxides 1 with methylisothiocyanate proceeds regio- and diastereoselectively to give tetrahydroimidazo[1,5-b][1,2,4]oxadiazol-2(1 H)-thiones 3 in high yields. The cis configuration of the adducts were proved by our double cis elimination test as well as by NOESY experiments The imidazooxadiazol-2-thiones 3a-e were treated with concentrated HCl in ethanol at 50degreesC to give the corresponding 4 H[1,2,4]oxadiazole-5-thione only in the cases where the substituent at C-6 is an aryl.